an attempt to model a has_many :through with factory girl ...

gistfile1.rb

# app/models/user.rb
class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable, :confirmable,
         :recoverable, :rememberable, :trackable, :validatable

  # Setup accessible (or protected) attributes for your model
  attr_accessible :email, :password, :password_confirmation, :remember_me
  # attr_accessible :title, :body
  
  has_many :staff_memberships
  has_many :publications, :through => :staff_memberships
end

# app/models/publication.rb
class Publication < ActiveRecord::Base
  attr_accessible :description, :title

  has_many :staff_memberships
  has_many :users, :through => :staff_memberships

  validates :users, :length => { :minimum => 1, :too_short => "a publication must have at least one user" }
end

# app/models/staff_membership.rb
class StaffMembership < ActiveRecord::Base
  attr_accessible :publication_id, :user_id

  belongs_to :user
  belongs_to :publication
end

# test/factories.rb
FactoryGirl.define do
  factory :user do
    sequence(:email) { |n| "user#{n}@suremail.info" }
    # encrypted_password { User.new.send(:password_digest, 'motorcycle!') }
    password "motorcycle!"
    password_confirmation "motorcycle!"
    confirmed_at { Time.now }
  end

  factory :publication do
    title "Entasis"
    description "A small literary journal."
    after :create do |pub|
      pub.users << FactoryGirl.create(:user)
    end
  end

  factory :staff_membership do
    user
    publication
  end
end